Method of processing electric arc furnace dust and providing fuel for an iron making process

ABSTRACT

The present invention provides a method for processing environmentally undesirable materials including petroleum coke and the sulfur and heavy metals contained therein and agglomerated waste dust from an electric arc furnace and the zinc, cadmium, lead and iron oxides contained therein and of providing fuel and a charging material for a process of making molten iron or steel preproducts and reduction gas in a melter gasifier. Metallized arc furnace waste dust material from a reduction furnace is introduced into the melter gasifier. The petroleum coke, oxygen and metallized waste dust material are reacted to produce reduction gas and molten iron from the iron oxides in the waste dust material. The molten iron contains the metals freed from combustion of the petroleum coke. The reduction gas is removed from the melter gasifier for use in the reduction furnace to produce an top off gas containing vapors of zinc, cadmium and lead.

BACKGROUND OF THE INVENTION

The invention relates to a method for processing environmentallyundesirable materials including petroleum coke and the sulfur and heavymetals contained therein and waste dust from an electric arc furnace andthe cadmium, lead, zinc and iron oxide contained therein to provide fueland a charging material for a process of making molten iron or steelpreproducts and reduction gas in a melter gasifier.

Electric arc furnaces utilize scrap to make steel products. Scrap ironor steel typically has zinc, cadmium and lead contained therein. Thesematerials cause a disposal problem when the scrap steel is processed inan electric arc furnace. The zinc, cadmium and lead are collected in awaste material known as electric arc furnace dust. Electric arc furnacedust is classified as a hazardous waste material and heretofore has beendisposed of in hazardous waste dumps. It has been estimated that thereare approximately 2 million tons per year of electric arc furnace dustaccumulated in the United States. Disposal of electric arc furnace dustin a hazardous waste dump may cost upwards of $150 to $200 per ton.

Petroleum coke is a product of refinery operations and is produced inthe United States utilizing three types of coke processing technology.Specifically these technologies as known to one skilled in the art aredelayed, fluid and flexi. By far most petroleum coke in the UnitedStates is produced using delayed technology. In 1990, according to theU.S. Department of Energy, 55 refineries in the United States which hadcoking facilities and a refinery capacity of 8 million barrels per dayproduced slightly over 76,000 short tons per day of petroleum coke. Theresidual petroleum coke produced amounted to about 6% by weight of eachbarrel of crude oil processed by the refineries.

Petroleum coke is generally the bottom end of refinery operations aftermost of the light ends and oils have been recovered from the originalcrude. The make up of petroleum coke will vary depending on a number offactors including the crude being processed and the process beingutilized. Generally on a dry basis petroleum coke will be composedlargely (approximately 90%) of fixed carbon and typically include sulfur(0.05% to 6%) and nitrogen (2% to 4%). Various metals typicallyIncluding vanadium, iron and nickel are found in petroleum coke.Usually, a typical petroleum coke contains about 10% volatile matter.Petroleum coke contains up to 10 to 15% moisture before drying.

Petroleum coke is produced either as blocky sponge coke or needle cokefrom delayed cokers or in a shot size form from fluid bed cokers. Spongecoke from delayed cokers is by far the most important coke produced inthe United States. Calcined sponge coke is used primarily in themanufacture of graphite electrodes, anodes and shaped products.Approximately one-fourth of the sponge coke production is used in theseproducts.

Until recent years the remainder of the petroleum coke in the U.S. wasused as fuel for power plants and cement kilns. However due to the highsulfur content, the need for blending with coal to maintain ignition andflame stability and environmental problems , petroleum coke has becomeless suitable as a boiler fuel. The high sulfur content of petroleumcoke also poses problems for cement kilns. Excess sulfur will causefinished concrete to expand and crack and also influences setting time.The high vanadium content also poses refractory problems. Thus there isa substantial amount of excess petroleum coke which must be disposed-The high sulfur content and the relatively high amounts of metals suchas vanadium and nickel make such disposal a real environmental problemwhich the present invention is directed to solving.

U.S. Pat. No. 4,849,015 to Fassbinder et al. discloses a method fortwo-stage melt reduction of iron ore, in which iron ore is prereducedsubstantially to wustite and at the same time melted down in a meltingcyclone, and then liquid hot metal is produced in an iron bath reactorconnected to the outlet of the melting cyclone and receiving the meltedwustite by adding carbonaceous fuels and oxidizing gas to the melt. Theresulting reaction gas from the melt is afterburned, and the dust-laden,partly burned reaction gases from the iron bath reactor are acceleratedand further afterburned by adding a hot blast with a temperature of 800°C. to 1500° C., and at least a portion of such accelerated, after burnedreaction gases are introduced into the melting cyclone to reduce andmelt fresh iron ore.

Carbonaceous fuels, such as coke, carbonized lignite, petroleum coke,etc., but preferably coal of varying quality, are fed to the melt in theiron bath reactor. Slag-forming additives, such as lime, fluorspar,etc., are also fed to the iron melt to set the desired slag composition.Although it is irrelevant for the present invention whether thesesubstances are introduced into the melt on the bath surface or frombelow the bath surface, it is preferable to add them through underbathfeed nozzles.

U.S. Pat. No. 4,806,158 to Hirsch et al. discloses a process for theproduction of reduced iron oxide-containing materials. Iron oxide andsolid carbonaceous reducing agent are charged into a first expandedfluidized bed, which is supplied with an oxygen-containing fluidizinggas. The gas residence time selected is controlled in the reactorcontaining the first fluidized bed so that the reduction potential willresult in a reduction of the iron oxide material not in excess of theFeO stage. A gas-solids suspension discharged from the first fluidizedbed is supplied to a second expanded fluidized bed, which is suppliedwith a strongly reducing fluidizing gas. Strongly reducing gas and amajor portion of the resulting devolatilized carbonaceous material aredischarged from the upper portion of the second fluidized bed. Reducedmaterial having a metallization of 50 to 80% and the remainingdevolatilized carbonaceous material are discharged from the lowerportion of the second fluidized bed. Suitable carbonaceous materialsinclude all coals, from anthracite to lignite, carbonaceous minerals andwaste products, such as oil shale, petroleum coke or washery refuse,provided that they are solid at room temperature. The oxygen-containinggas preferably consists of oxygen or of oxygen-enriched air.

U.S. Pat. No. 4,897,179 to Mori et al. provides a method of producingreduced iron and light oil from iron ore and heavy oil which comprises athermal cracking step of subjecting heavy oil to thermal cracking whileretaining iron ore particles in a fluidized state to produce light oiland simultaneously to deposit coke as by-product on the surface of theiron ore particles; a gasification step of putting the coke-depositedore in contact with an oxidizing gas including steam and oxygen in afluidized state to react the coke with the gas thereby to produce areducing gas containing hydrogen and carbon monoxide and of heating thecoke-deposited ore upward of a reduction temperature of iron ore bypartial oxidization of the coke; and a reduction step of reducing thecoke-deposited iron ore in a fluidized state by the reducing gas toproduce reduced iron. When the gasification step is performed by anoxidizing gas containing a majority of steam and up to 15 vol. %, basedon the steam, of oxygen at 800°-1000° C. under a pressure of 0-10 kg/cm²G, a reducing gas containing high-concentration hydrogen gas isobtained.

Slags of high sulfur capacity have been utilized in applicationsassociated with ferrous metallurgy. Kleimeyer et al. in U.S. Pat. No.4,600,434 describe the use of high sulfur capacity slag and magnesiummetal to desulfurize molten iron while it is contained in a torpedo car.Quigley, U.S. Pat. No. 4,853,034, describes using a vanadium-bearing,high-magnesia synthetic calcium aluminate slag for absorbing sulfurduring ladle refining of steel. Knauss et al., U.S. Pat. No. 4,695,318,describe using a synthetic slag similar to that of U.S. Pat. No.4,853,034, and the refractory brick of the ladle itself, to desulfurizemolten iron contained in said ladle.

In recent years methods utilizing a melter gasifier have been developedto produce molten iron or steel preproducts and reduction gas. Most ofthese processes utilize a coal fluidized-bed. A high temperature isproduced in the melter gasifier utilizing coal and blown in oxygen toproduce a fluidized bed and iron sponge particles are added from aboveto react in the bed to produce the molten iron.

Thus in European Patent B1-0010627, a coal fluidized-bed with ahigh-temperature zone in the lower region is produced in a meltergasifier, to which iron sponge particles are added from above. Onaccount of the impact pressure and buoyancy forces in the coalfluidized-bed, iron sponge particles having sizes greater than 3 mm areconsiderably braked and substantially elevated in temperature by theheat exchange with the fluidized bed. They impinge on the slag layerforming immediately below the high-temperature zone at a reduced speedand are melted on or in the same. The maximum melting performance of themelter gasifier, and thus the amount and temperature of the molten ironproduced, not only depends on the geometric dimensions of the meltergasifier, but also are determined to a large extent by the quality ofthe coal used and by the portion of larger particles in the iron spongeadded. When using low-grade coal, the heat supply to the slag bath, andthus the melting performance for the iron sponge particles, declineaccordingly. In particular, with a large portion of iron spongeparticles having grain sizes of about 3 mm, which cannot be heated tothe same extent as smaller particles by the coal fluidized-bed whenbraked in their fall and which, therefore, necessitate a higher meltingperformance in the region of the slag layer, the reduced meltingperformance has adverse effects in case low-grade coal is used.

A melter gasifier is an advantageous method for producing molten iron orsteel preproducts and reduction gas as described in U.S. Pat. No.4,588,437. Thus there is disclosed a method and a melter gasifier forproducing molten iron or steel preproducts and reduction gas. A firstfluidized-bed zone is formed by coke particles, with a heavy motion ofthe particles, above a first blow-in plane by the addition of coal andby blowing in oxygen-containing gas. Iron sponge particles and/orpre-reduced iron ore particles with a substantial portion of particlesizes of more than 3 mm are added to the first fluidized-bed zone fromabove. A melter gasifier for carrying out the method is formed by arefractorily lined vessel having openings for the addition of coal andferrous material, openings for the emergence of the reduction gasesproduced, and openings for tapping the metal melt and the slag. Pipes ornozzles for injection of gases including oxygen enter into the meltergasifier above the slag level at at least two different heights.

Another process utilizing a melter gasifier is described in U.S. Pat.No. 4,725,308. Thus there is disclosed a process for the production ofmolten iron or of steel preproducts from particulate ferrous material aswell as for the production of reduction gas in the melter gasifier. Afluidized-bed zone is formed by coke particles upon the addition of coaland by blowing in oxygen-containing gas by nozzle pipes penetrating thewall of the melter gasifier. The ferrous material to be reduced isintroduced into the fluidized bed. In order to be able to produce molteniron and liquid steel preproducts in a direct reduction process with alower sulfur content of the coal used, the ferrous material to bereduced is supplied closely above the blow-in gas nozzle plane producingthe fluidized bed. An arrangement for carrying out the process includesa melter gasifier in which charging pipes penetrating its wall areprovided in the region of the fluidized-bed zone closely above the planeformed by the nozzle pipes. The ferrous material to be melted as well asthe dusts separated from the reduction gas and, if desired, fluxescontaining calcium oxide, magnesium oxide, calcium carbonate and/ormagnesium carbonate are introduced therethrough.

There is also a process known as the COREX® process (COREX® is atrademark of Deutsche Voest-Alpine Industrieanlagenbau GMBH andVoest-Alpine Industrieanlagenbau). This process is described inSkilling's Mining Review, Jan. 14, 1989 on pages 20-27. In the COREX®process the metallurgical work is carried out in two process reactors:the reduction furnace and the melter gasifier. Using non-coking coalsand iron bearing materials such as lump ore, pellets or sinter, hotmetal is produced with blast furnace quality. Passing through a pressurelock system, coal enters the dome of the melter gasifier wheredestructive distillation of the coal takes place at temperatures in therange of 1,100°-1,150° C. Oxygen blown into the melter gasifier producesa coke bed from the introduced coal and results in a reduction gasconsisting of 95% CO+H₂ and approximately 2% CO₂. This gas exits themelter gasifier and is dedusted and cooled to the desired reductiontemperature between 800° and 850° C. The gas is then used to reduce lumpores, pellets or sinter in the reduction furnace to sponge iron havingan average degree of metalization above 90%. The sponge iron isextracted from the reduction furnace using a specially designed screwconveyor and drops into the melter gasifier where it melts to the hotmetal. As in the blast furnace, limestone adjusts the basicity of theslag to ensure sulfur removal from the hot metal. Depending on the ironores used, SiO₂ may also be charged into the system to adjust thechemical composition and viscosity of the slag. Tapping procedure andtemperature as well as the hot metal composition are otherwise exactlythe same as in a blast furnace. The top gas of the reduction furnace hasa net calorific value of about 7,000 KJ/Nm³ and can be used for a widevariety of purposes.

The fuels used in these processes are typically described as a widevariety of coals and are not limited to a small range of coking coal.The above-noted article from Skilling's Mining Review notes thatpetroleum coke suits the requirements of the COREX® process. Brown coaland steam coal which are relatively poor quality coal having arelatively high ash content i.e. plus 15%, have been identified assuitable for use in these processes. Coke made from coal has also beenidentified as a fuel for many of the processes utilizing meltergasifiers.

RELATED APPLICATIONS

This application is a related to applications Ser. No. 07/958,043 filedOct. 6, 1992; Ser. No. 07/991,914, filed Dec. 17, 1992, and Ser. No.08/056,341, filed Apr. 30, 1993.

SUMMARY OF THE INVENTION

The present invention is directed to a solution for the disposal of twoenvironmentally objectionable materials and provision of a new andunexpectedly superior fuel source and of a ferrous material source forprocesses utilizing melter gasifiers to make molten iron or steelpreproducts.

In accordance with the invention it has been found that petroleum cokemakes an excellent source of carbon in processes making molten iron orsteel preproducts in which a melter gasifier unit is used. Further,electric arc furnace dust provides a source of iron oxide which can beconverted to molten iron as well as non-ferrous heavy metal oxides ofzinc, cadmium and lead which can be concentrated and recovered in theprocess. Moreover, the reaction in these processes utilizing thepetroleum coke as a fuel in the melter gasifier tends to combust thepetroleum coke substantially completely with hot reduction gas as theonly gaseous product. The hot reduction gas from the molten gasifier at850° C. is recycled to the primary reduction furnace where the ironoxide in the electric arc furnace dust is metallized and the oxides ofzinc, cadmium and lead are reduced to metal and vaporized. The top offgas from the reduction furnace contains the metallized vapors of thezinc, cadmium and lead from the electric arc furnace dust. When the topoff gas is scrubbed with water, the zinc, cadmium and lead are recoveredin the gas washer sludge at concentrations up to 50% for metal recycleand refining. Residual sulfur from the petroleum coke is discharged as asulfide in the slag formed in the melter gasifier and is removed anddisposed of with the slag. Heavy metals from the petroleum coke arecarried over in stable form in solution in the molten iron or steelpreproducts and will solidify therewith.

In a broad aspect, the invention provides a method for processingenvironmentally undesirable materials including petroleum coke and thesulfur and heavy metals contained therein and waste dust from anelectric arc furnace and the zinc, cadmium, lead and iron oxidescontained therein and of providing fuel and a charging material for aprocess of making molten iron or steel preproducts and reduction gas ina melter gasifier. A melter gasifier is provided and has an upper fuelcharging end, a reduction gas discharging end, a lower molten metal andslag collection end. Entry means are provided for charging material intothe melter gasifier. Petroleum coke is introduced into the meltergasifier at the upper fuel charging end. Oxygen-containing gas is blowninto the petroleum coke to form at least a first fluidized bed of cokeparticles from the petroleum coke. Arc furnace waste dust material isagglomerated and charged into the reduction furnace through the entrymeans. Petroleum coke and oxygen are reacted in the melter gasifier topartially combust the major portion of the petroleum coke to producereduction gas which is directed to the reduction furnace. In thereduction furnace, the reduction gas reduces the metals forming metalvapors of zinc, cadmium and lead in the reduction top off gas andmetallized iron from iron oxide in the waste dust material. Themetallized iron is discharged hot to the melter gasifier for meltingwith petroleum coke and oxygen. The molten iron contains heavy metalsfreed from combustion of the petroleum coke. A slag is producedcontaining sulfur freed from combustion of the petroleum coke. Thereduction top gas including the metal vapors contained therein areremoved from the reduction furnace. Preferably the zinc, cadmium andlead metals from the metal vapors contained in the reduction gas arerecovered and reused.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram illustrating the present invention;

FIG. 2 is a schematic vertical section of a melter gasifier useful inaccordance with the present invention; and

FIG. 3 is a schematic flow sheet illustrating the COREX® process inwhich the method of the present invention is particularly useful.

OBJECTS OF THE INVENTION

It is a particular object of the present invention to provide a processfor both disposing of two environmentally undesirable materials andproviding a novel fuel and ferrous material feedstock for an iron makingprocess which utilizes a melter gasifier. Other objects and advantagesof the present invention will be apparent from the following detaileddescription read in view of the accompanying drawings which are made apart of this specification.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is predicated on the recognition that petroleum coke canadvantageously replace coal or coke made from coal which heretofore wasused as a source of carbon in iron making processes wherein a meltergasifier is used and that electric arc furnace dust can be effectivelydisposed of in such a process while providing a source of ferrousmaterial for use in iron making. Further, in accordance with theinvention zinc, cadmium or lead may be recovered as a byproduct. Inaddition, the use of petroleum coke in the iron making process in amelter gasifier substantially completely combusts the petroleum cokethus solving an environmentally sensitive disposal problem. Sulfur andheavy metals which are contained in petroleum coke are also safelydisposed of in accordance with the invention. Further, electric arc dustwhich is classified as a hazardous waste because of the zinc, cadmiumand lead components can be safely and economically disposed of in theprocess while providing a source of ferrous material for ironproduction. The sludge resulting from the process provides aconcentrated source of zinc, cadmium and lead oxides from which themetals can be removed. The reduction furnace is operated at a top gastemperature of at least 400° C., such that the metal vapors do notcondense until entering the top gas scrubber. Along with entrainedcarbon and metallic iron dust the metal bearing sludge from the scrubberis dewatered and marketed to a recycling refiner.

FIG. 1 is a flow diagram illustrating the method of refining crude oiland producing steel in an environmentally desirable manner whereinundesirable materials resulting in such production, namely petroleumcoke and electric arc furnace dust, are disposed of in an iron makingprocess. Petroleum feedstock 30 is introduced into a refinery 32 whereoil and gas products 34 are produced. The residual coke from therefinery 32 is passed to a delayed coker unit 36 where petroleum coke 38is produced. Volatiles from the process are returned to the oil and gasproducts via conduit 39. The petroleum coke amounts to about 6% byweight of the petroleum feedstock being processed.

Heretofore, disposal of the petroleum coke has been a significantproblem. However, in accordance with the invention, disposal of thepetroleum coke is accomplished in an advantageous manner as a fuel in aniron-making process where a melter gasifier is utilized. Thus, petroleumcoke is introduced as a fuel into melter gasifier 40 for combustion withoxygen and metallic iron from source 42 which has been reduced fromelectric furnace dust in reduction furnace 44. Liquid iron containingheavy metals freed from the combustion of the petroleum coke isrecovered in collection vessel 42 for later steel making 44. Anreduction gas rich in CO is produced from the melter-gasifier and may bedirect to the reduction furnace 44 and used in direct reduction of ironor as export gas 46 and used as a fuel for power production 48. Slag iswithdrawn from the melter gasifier at slag collection vessel 50. Theslag contains the sulfur freed from the combustion of the petroleumcoke. Slag is disposed of; for example, by forming construction products52.

An electric arc furnace 31 is useful to produce steel products 35 fromautomotive scrap 33 which is the principal ferrous material used tocharge electric arc furnaces. Automotive scrap contains a significantamount of zinc, cadmium and lead and this material is collected in theelectric arc furnace dust as a waste material from the electric arcfurnace steelmaking process.

Thus, due to the use of "automotive scrap" feed, electric arc furnacesproduce a waste product having high concentration of non-ferrous metals.Arc furnace "dust" includes zinc, cadmium and lead metals. The materialhas been designated a hazardous waste and is therefore increasingly adisposal problem for operators Present disposal costs range betweenabout $150 and $200 per ton of "dust." Electric arc furnace dusttypically contains 5% of zinc and can contain up to 20% of zincdepending on scrap quality. Residuals of cadmium and lead, up to 1%, arecontained with the zinc contamination.

The electric arc furnace dust from the furnace baghouse contains asignificant amount of up to (95%) of a combination of iron oxide, limeand silica, in addition to the hazardous non-ferrous metals of concern.Iron oxide content is commonly about 50% by weight. The waste materialmay be agglomerated with lime and/or Portland cement, allowed to age togain strenght and charged to a COREX® reduction furnace which is coupledto a melter-gasifier for producing molten iron. At the reductiontemperature of around 850° C., the volatile non-ferrous metals arevaporized and carried as top reduction gas to the off-gas scrubber 45from the reduction furnace and captured in the sludge 47.

Through the process of this invention, the quantity of arc furnace wastemay be reduced to about 5% of the total dust volume now being disposedof in hazardous waste landfills. Moreover, due to a concentration ofmetals, recovery of metal value is possible from the gas scrubbersludge. The sludge will consist of approximately one-half non-ferrousmetals and the other half of about equal parts of metallic iron andcarbon dust.

Electric arc furnace dust can be accumulated and agglomerated near aniron making site to be charged to the reduction furnace in "campaign"fashion during a pre-selected period of the iron making program withsegregation of the non-ferrous metal sludge. Since the metals arevaporized and the gases present are reducing, the volatilized metalvapors will be transported through the pellet bed in the reductionfurnace 44 as fume to the reduction furnace top gas duct which is heatedto prevent metal condensation, and thereafter to the water based gasscrubber 45 for elimination as "campaign" scrubber sludge 47.

The quantity of scrubber sludge may be segregated from "non-campaign"non-ferrous metal free scrubber sludge which is dried and directlyrecycled to the melter gasifier. The quantity of the non-ferrous metal"campaign" scrubber sludge is about one twentieth of the initialquantity of electric arc furnace waste charged to the COREX® process.Because non-ferrous metals may be present in the top gas duct work andcondense on the metal lining, the metal duct work connecting thereduction furnace 44 with scrubber 46 is preferably heated to at leastor about 400° C. during campaign operation. Due to the concentratedmetals content of the scrubber sludge, it may be viable to furtherprocess the sludge to recover the metals content.

In one form, the invention provides for "campaigning" the process ofusing electric arc furnace dust as the ferrous material feed for theCOREX® process with the more conventional use of iron ore as the feedfor the process. Thus, molten iron might be produced using petroleumcoke and iron ore in a COREX® process for a given time period, forexample three weeks to a month, then electric arc furnace dust, suitablyagglomerated, is used to replace the iron ore as the feed to thereduction furnace in the COREX® process for a time period, for example aweek, to process the electric arc furnace dust on hand. A scheduled of11 consecutive months of using iron ore as the feed and 1 month ofelectric arc furnace dust is preferred. After this is accomplished, ironore replaces the dust as the ferrous material in the process. Theelectric arc furnace dust is agglomerated into discrete particles about1/2 inch in size, similar to iron ore pellets, using a bonding agentsuch as lime on Portland cement mixed with the dust for feed to apelletizing apparatus.

FIG. 2 schematically illustrates a melter gasifier useful with thepresent invention. The melter gasifier, generally indicated by thenumeral 1 has side walls 2 which are refractory lined on their innersides. The hood 3 of the melter gasifier 1 has three openings 4, 5 and6. In accordance with the opening 4 is adopted for charging petroleumcoke 7 of various grain or piece sizes into the interior of the meltergasifier. Particulate ferrous material 8 preferably iron sponge from thereduction furnace, is charged into the melter gasifier through theopening 5. It is suitable to supply the iron sponge at an elevatedtemperature. In accordance with the present invention, the supply ofsponge iron may be interrupted and electric arc furnace dust which hasbeen reduced in the reduction furnace may be charged into the moltergasifier. To carry away the reduction gas which is formed during thereaction in the melter gasifier, a conduit 9 is provided extending outof opening 6. The reduction gas carried away may be is used in manyprocesses to pre-reduce or reduce oxidic iron ore or electric arcfurnace dust. It is advantageously used in the reduction furnace coupledto the melter gasifier.

In general the melter gasifier comprises a lower section A, a centralsection B, an intermediate section C between sections A and B and anupper section D above the central section B, whose cross section iswidened and which serves as an expansion zone. In the bottom region ofthe lower section A of the melter gasifier 1, which serves to collectmolten metal and liquid slag including any sulfur residue from thecombustion of petroleum coke, a tapping opening 10 for the melt 11 isprovided in the wall 2. Further up the wall, there is an opening 12 forthe slag tap in the lower section A. Alternatively, the slag may betapped with the metal and separated outside the melter gasifier. In thelower region of the central section B of the melter gasifier 1, a nozzlepipe 14 is inserted through an opening 13 in the wall 2.Oxygen-containing carrier gas is injected into the melter gasifierthrough nozzle pipe 14. If desired, carbon carriers can be introducedinto the melter gasifier 1 in a first horizontal blow-in plain 15.

Preferably, a plurality of openings 13 with nozzle pipes 14 are presentat this location spaced around the melter gasifier. In the centralsection B, a first fluidized bed zone 16 may be formed by coke particlesfrom con, busted petroleum coke. The intermediate section C, which, inthe embodiment illustrated, is cylindrically designed, is provided toaccommodate a second zone 17 of a fluidized bed formed by coke particlesfrom combustion the petroleum coke. Generally, the coke particles in thefluidized bed in this section of the melter gasifier will have lessmotion than those in section B. Through the wall of the intermediatesection C, gas supply means, in the present case nozzle pipes or tuyeres19, are inserted . The tuyeres are positioned to direct the gases towardthe central axis 18 of the melter gasifier. The tuyeres are adapted forinjecting oxygen-containing gas and carbon carriers into the meltergasifier. They project into the second zone 17 of coke particles, endingclosely above the slag layer 20. Just one nozzle pipe 19 has beenillustrated in FIG. 2 depending on the size of the melter gasifier, 10to 40 preferably 20 to 30, nozzle pipes 19 may be provided, and locatedsubstantially in a second horizontal blow-in plane 21. The nozzle pipes19 are arranged so as to be vertically pivotable in the direction of thedouble arrow 22. Also the nozzle pipes 14, through which the carrier gasand additional fuel flow into the first fluidized-bed zone 16 aredesigned to be vertically pivotable with the embodiment of the inventionillustrated.

The ferrous material 8 which as noted may be sponge iron or reducedelectric arc furnace dust from the reduction furnace introduced throughthe opening 5 at first reaches the first fluidized-bed zone 16 afterhaving fallen through the upper section D of the melter gasifier whichserve as an expansion zone, in which the ferrous material is slowed andheated. The ferrous material may comprise iron ore or alternativelyelectric arc furnace dust in a batch type process. Smaller particlesmelt, drop through the second zone 17 of coke particles and descend intothe lower section A. Larger particles at first remain lying on thesecond zone 17 or are held fast in the uppermost layer of this zone,until they are also melted upon the action of the high temperatureprevailing in the region of the first blow-in plane 15. In the secondzone, the downwardly dropping metal melt is super-heated and, ifdesired, may be treated by the reaction of fine particle fluxes, whichare introduced through the nozzle pipes 19. The metal melt 11 tappedthrough the opening in 10 is sufficiently hot in order to be subjectedto further metallurgical aftertreatments. Above the melt 11, a layer ofliquid slag 20 collects. The liquid slag may be stripped off via the tapopening 12. The petroleum coke particles, during operation of the meltergasifier, must be continuously supplemented through the opening 4 withlarger pieces, which are preferably used to build up the second zone 17,after falling through the first zone 16. The melter gasifier shown inFIG. 2 and the prior art operation using coal or coke produced from coalare described in U.S. Pat. No. 4,588,437.

Refer now to FIG. 3 which is a schematic flow sheet of the COREX®process in which the method of the invention is particularly useful. TheCOREX® process utilizes a melter gasifier substantially similar to themelter gasifier of FIG. 2 and is generally indicated in FIG. 3 by thenumeral 100. The COREX® process is designed to operate under elevatedgas pressures up to five bar. The process pressure is supplied from theintegral oxygen production facility which supplies oxygen through thetuyeres 119 on the COREX® melter gasifier 100. Gasifier gas pressurefrom the melter gasifier 100 operates the primary direct reductionfurnace 126 for iron ore reduction to sponge iron when the process isbeing run with iron ore. Alternatively, electric arc dust may be reducedin the direct reduction furnace.

Charging of petroleum coke to the melter gasifier 100 is accomplishedthrough a pressurized lock hopper 128. The iron ore or electric arcfurnace dust is supplied to the reduction furnace 126 through a similarlock hopper 121 in a manner well known to those skilled in the art. Thepetroleum coke is stored in a pressurized bin and charged into themelter gasifier by suitable means such as speed controlled feed screw134.

Upon entering the dome of the melter gasifier 100, at entry port 101,the 10% of residual hydrocarbons contained in the petroleum coke areflashed off at 1100° C. and cracked in the reducing atmosphere to CO andH₂. The calcined petroleum coke particles are rapidly heated to 1100° C.and descend with the hot reduced iron particles and hot calcined limeparticles from the reduction furnace 126 to the dynamic fluidized bed.The calcined petroleum coke (essentially all carbon) is gasified into COwhich rises to the gasifier gas outlet 119.

When electric arc furnace dust is utilized, with the high temperaturereduction gas (850° C.) and rich reducing conditions in the reductionfurnace 126, the zinc, cadmium and lead from the electric arc furnituredust will be vaporized and be transported in the reduction furnace topoff gases out exit 127. Since the non-ferrous metals are vaporized andthe off gas stream is reducing, the metal vapors will be transportedinto the heated reduction furnace top gas duct work 137 to the top gasscrubber 129. The duct work 137 between the reduction furnace 126 andthe top gas scrubber 129 should be heated to at least 400° C. to preventcondensation on the duct. With heated duct work, the non-ferrous metalswill be transferred to the wet scrubber 129 and eliminated as sludge invessel 141. Alternatively, with heated duct work and a liquid metalreservoir 143 ahead of the scrubber, the metal vapors can be condensedseparately from the sludge and collected as a marketable metal product.

The iron particles are melted in the dynamic particle bed 116 and dropto a molten liquid iron pool 111 accumulated below the oxygen tuyeres119 on the melter gasifier hearth 114. The silica and alumina oxidecontent of the sponge iron is fluxed and melted with the calcined limein the bed to form liquid slag droplets which descend and form a liquidslag layer 113 covering the liquid iron pool 111. The liquid iron andslag are periodically tapped and removed through a taphole 110 from themelter gasifier hearth.

As the calcined coke burns at a high temperature with oxygen above thetuyeres 119, an oxidizing coolant, such as steam or CO₂, or both areinjected at the tuyere level to maintain the melter gasifier dometemperature of 1100° C. The injected coolants create additional reducinggas with hydrogen forming from reduction of the steam and CO formingfrom the reduction of the CO₂. The combined reducing gases rise to thegasifier gas outlet main 119 at 1100° C. where they are tempered with aside stream from the cooling gas scrubber 109 and cooling gas blower 140via line 103 to 850° C. before passing to the hot cyclone 115 and thereduction furnace 126. The gasifier gas cooling is useful to avoidfusion and maintain discrete free flowing particles in the column of thereduction shaft furnace 126. Overheating will cause clusters or clinkersto form inside the shaft furnace with disruption of the furnace solidsand gas flow.

After being cooled in the cooling gas scrubber 109 and cleaned of dustin the hot cyclone 115, the gasifier gas is passed upward in thereduction furnace 126 through the descending bed of ferrous material,either iron ore or agglomerated electric arc furnace dust, converting itto metallic sponge iron and carburizing the reduced iron to a level ofthree to five percent prior to hot discharge to the melter gasifier 100.The gasifier gases are partially consumed by the reaction in thereduction furnace and discharged at 127 as furnace top gas at 400° C.The top gases are cleaned in the top gas wet scrubber 129, removingwater vapor formed during iron ore reduction and discharged as exportgas 131 at 40° C. The export gas is low in particulates containing 25%of CO₂.

The highly preferred mode of the present invention utilizes petroleumcoke in combination with a melter gasifier. The reduction gas from themelter gasifier is used in the reduction furnace to reduce the electricarc furnace dust to vaporize the non-ferrous metals, i.e., zinc, cadmiumand lead, contained in the dust and to reduce the iron oxide containedin the dust. It is noted that coal or metalurgical coke could be used inplace of petroleum coke as the fuel in the melter gasifier. Further theprocess of removing the non-ferrous metals could be carried out in areduction furnace without need for a melter gasifier using a differentsource of hot reduction gas to vaporize the zinc, cadmium and lead. Forexample a suitable source of hot reduction gas would be the hot gasresulting from natural gas reforming.

The present invention provides a method for processing environmentallyundesirable materials including petroleum coke and the sulfur and heavymetals contained therein and waste dust from an electric arc furnace andthe cadmium, lead, zinc and iron oxide contained therein and ofproviding fuel and a charging material for a process of making molteniron or steel preproducts and reduction gas in a melter gasifier. Amelter gasifier is provided and has an upper fuel charging end, areduction gas discharging end, a lower molten metal and slag collectionend. A reduction furnace is operably connected to the melter gasifiers.An entry is formed for charging metallized ferrous material into saidmelter gasifier from a reduction furnace. Petroleum coke is introducedinto the melter gasifier at the upper fuel charging end andoxygen-containing gas is blown into the petroleum coke to form at leasta first fluidized bed of coke particles from the petroleum coke.Vaporized zinc, cadmium and lead from the electric arc furnace wastedust material which has been processed in the reduction furnace isremoved with the top off gas. Metallized iron oxides are introduced intothe melter gasifier through the material changing entry means. Thepetroleum coke, oxygen and metallized iron oxides from waste dustmaterial are reacted to combust the major portion of the petroleum coketo produce reduction gas and molten iron. The molten iron contains theheavy metals freed from combustion of the petroleum coke. A slag isformed containing sulfur freed from combustion of the petroleum coke.The reduction gas is removed from the melter gasifier and use in thereduction furnace.

The principles, preferred embodiments and modes of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments disclosed. Theembodiments are to be construed as illustrative rather than restrictive.Variations and changes may be made by others without departing from thespirit of the present invention. Accordingly, all such variations andchanges which fall within the spirit and scope of the present inventionas defined in the following claims are expressly intended to be embracedthereby.

What is claimed is:
 1. A method for processing environmentallyundesirable materials including petroleum coke and the sulfur and heavymetals contained therein and waste dust from an electric arc furnace andthe zinc, cadmium, lead and iron oxides contained therein and ofproviding fuel and a charging material for a process of making molteniron or steel preproducts and reduction gas in a melter gasifier whichmethod comprises providing a melter gasifier having an upper fuelcharging end, a reduction gas discharging end, a lower molten metal andslag collection end, and means providing an entry for charging materialinto said melter gasifier; providing a reduction furnace operablyconnected to said entry for charging materials into said meltergasifier; introducing petroleum coke into said melter gasifier at saidupper fuel charging end; blowing oxygen-containing gas into thepetroleum coke to form at least a first fluidized bed of coke particlesfrom said petroleum coke; introducing metallized arc furnace waste dustmaterial from said reduction furnace into said melter gasifier throughsaid entry means, reacting petroleum coke, oxygen and metallized wastedust material to combust the major portion of the petroleum coke toproduce reduction gas and molten iron from iron oxides in said wastedust material, said molten iron containing heavy metals freed fromcombustion of the petroleum coke and a slag containing sulfur freed fromcombustion of the petroleum coke; and removing said reduction gas fromsaid melter gasifier and introducing said reduction gas into saidreduction furnace to metallize electric arc furnace dust in saidreduction furnace and to produce a top off gas containing metal vaporsof non-ferrous metals contained in said electric arc furnace dust. 2.The method of claim 1 further characterized by recovering at least oneof the non-ferrous metals from the metal vapors contained in said topoff gas from said reduction furnace.
 3. An improvement to a molten ironmaking process comprising the steps of introducing petroleum coke into amelter gasifier; blowing oxygen containing gas into said melter gasifierand combusting petroleum coke to form at least a first fluidized bed ofcoke particles from said petroleum coke; charging reduced iron ore intosaid melter gasifier through an entry port in the upper portion thereof;reacting petroleum coke, oxygen and reduced iron ore in said meltergasifier to combust the major portion of said petroleum coke to producereduction gas and molten iron containing heavy metals freed fromcombustion of the petroleum coke and a slag containing sulfur freed fromcombustion of the petroleum coke; flowing reduction gas out of saidmelter gasifier; combining said reduction gas with a side stream of coolreducing gas to form a cooled reduction gas; directing said cooledreduction gas to a reduction furnace which is operably connected to saidmelter gasifier and is charged with iron ore and mixing said cooledreduction gas with iron ore in said reduction furnace to reduce the ironore to metallic iron and to carbonize the metallic iron prior todischarging it to the melter gasifier for further processing and toproduce a top off gas; interrupting charging reduced iron ore into saidmelter gasifier; introducing arc furnace waste dust material into saidreduction furnace; vaporizing the non-ferrous metals contained in saidelectric furnace arc dust and reducing the iron oxides contained in saidelectric furnace arc dust; removing said vaporized non-ferrous metalswith the top off gas produced said reduction furnace; and introducingthe reduced iron oxides into melter gasifier through said entry means,reacting petroleum coke, oxygen and said reduced iron oxides dust tocombust the major portion of the petroleum coke to produce reduction gasand molten iron from said iron oxides, said molten iron containing heavymetals freed from combustion of the petroleum coke.
 4. The method ofclaim 3 further characterized in recovering at least one metal from thevaporized non-ferrous metals contained in said top off gas.
 5. Themethod of claim 3 further characterized in that said reduction gas ismixed with CO₂ in the melter gasifier prior to being removed from saidmelter gasifier to form a combined reducing gas.
 6. The method of claim4 further characterized in that the temperature of said combinedreducing gas leaving the melter gasifier is about 1100° C.
 7. The methodof claim 6 further characterized in that said combined reducing gas ismixed with a stream of cool reduction gas to form a mixed gas having atemperature of about 850° C. and flowing said mixed gas to a reductionfurnace.
 8. The method of claim 5 further characterized in that thetemperature of said combined reducing gas leaving the melter gasifier isabout 1100° C.
 9. The method of claim 8 further characterized in thatsaid combined reducing gas is mixed with a stream of cool reduction gasto form a mixed gas having a temperature of about 850° C. and flowingsaid mixed gas to a reduction furnace.
 10. An iron making processcomprising the steps of introducing petroleum coke into a meltergasifier; blowing oxygen containing gas into said melter gasifier andcombusting petroleum coke to form at least a first fluidized bed of cokeparticles from said petroleum coke; introducing reduced electric arcfurnace dust into said melter gasifier through an entry port in theupper portion thereof; reacting petroleum coke, oxygen and the reducedelectric arc dust in said melter gasifier to combust the major portionof said petroleum coke to produce reduction gas and molten ironcontaining heavy metals freed from combustion of the petroleum coke anda slag containing sulfur freed from combustion of the petroleum coke;flowing reduction gas out of said melter gasifier; combining saidreduction gas with a side stream of cool reducing gas to form a cooledreduction gas; directing said cooled reduction gas to a reductionfurnace which is operably connected to said melter gasifier, passingsaid cooled reduction gas upward through electric arc furnace dustagglomerates in said reduction furnace to reduced the electric arcfurnace dust and to form a top off gas; charging the reduced electricarc furnace dust into the melter gasifier for further processing andremoving the top gas from said reduction furnace.
 11. The method ofclaim 10 further characterized in that said reduction gas is mixed withsteam in the melter gasifier prior to being removed from said meltergasifier to form a combined reducing gas.
 12. The method of claim 10further characterized in that said reduction gas is mixed with CO₂ inthe melter gasifier prior to being removed from said melter gasifier toform a combined reducing gas.
 13. The-method of claim 11 furthercharacterized in that the temperature of said combined reducing gasleaving the melter gasifier is about 1100° C.
 14. The method of claim 13further characterized in that said combined reducing gas is mixed with astream of cool reduction gas to form a mixed gas having a temperature ofabout 850° C. and flowing said mixed gas to the reduction furnace. 15.The method of claim 12 further characterized in that the temperature ofsaid combined reducing gas leaving the melter gasifier is about 1100° C.16. The method of claim 15 further characterized in that said combinedreducing gas is mixed with a stream of cool reduction gas to form amixed gas having a temperature of about 850° C. and flowing said mixedgas to the reduction furnace.
 17. The method of claim 10 furthercharacterized in that water vapor is removed from said top gas prior toexport.
 18. A method of refining crude oil, making steel and producingmolten iron in an environmentally desirable manner comprising:formingpetroleum products from crude oil in a refinery utilizing a cokeprocessing plant, said coke processing plant producing petroleum cokeresidual including sulfur and hearty metal components; forming steel ina steel making process in an electric arc furnace; collecting electricfurnace arc dust formed in said steel making process; introducing thepetroleum coke into a melter gasifier; blowing oxygen containing gasinto said melter gasifier and combusting the petroleum coke to form atleast a first fluidized bed of coke particles from said petroleum coke;reducing the electric arc furnace dust; introducing the reduced electricarc furnace dust into said melter gasifier through an entry port in theupper portion thereof; reacting the petroleum coke, oxygen and reducedelectric arc dust in said melter gasifier to combust the major portionof said petroleum coke to produce reduction gas and to produce molteniron containing heavy metals freed from combustion of the petroleumcoke; flowing the reduction gas out of said melter gasifier; andreducing electric arc furnace dust with said reduction gas.
 19. A methodas recited in claim 18 wherein said petroleum coke is introduced withoutcoal.
 20. A method as recited in claim 18 wherein said reduction gas hasa CO level of about 70%.
 21. A method of refining crude oil, makingsteel and producing molten iron in an environmentally desirable mannercomprising:forming petroleum products from crude oil in a refineryutilizing a delayed coke processing plant, said coke processing plantproducing a petroleum coke residual including sulfur and heavy metalcomponents; producing steel in an electric furnace arc process whichprocess results in the formation of electric arc furnace dust containingnon-ferrous metals including zinc, cadmium and lead; introducing thepetroleum coke residual into a melter gasifier; blowing oxygencontaining gas into said melter gasifier and combusting the petroleumcoke residual to form at least a first fluidized bed of coke particlesfrom said petroleum coke; introducing reduced electric arc furnace dustinto said melter gasifier through an entry port in the upper portionthereof; reacting the petroleum coke residual, oxygen and the reducedelectric arc furnace dust in said melter gasifier to combust the majorportion of said petroleum coke residual to produce reduction gas and toproduce molten iron containing heavy metals freed from combustion of thepetroleum coke and a slag containing sulfur freed from combustion of thepetroleum coke; flowing reduction gas to a reduction furnace andreacting said reduction gas with electric arc furnace dust to reduce theelectric arc furnace dust and to form a top of gas containing vapors ofthe non-ferrous metals, flowing said top off gas contained in saidelectric arc furnace dust out of said reduction furnace through a heatedconduit to prevent condensation of said vapors, forming a sludgecontaining said non-ferrous metals and recovering at least onenon-ferrous metal from the sludge.